On Mon, Oct 14, 2024 at 11:12 AM Xuan Zhuo <xuanz...@linux.alibaba.com> wrote:
>
> Currently, the virtio core will perform a dma operation for each
> buffer. Although, the same page may be operated multiple times.
>
> In premapped mod, we can perform only one dma operation for the pages of
> the alloc frag. This is beneficial for the iommu device.
>
> kernel command line: intel_iommu=on iommu.passthrough=0
>
> | strict=0 | strict=1
> Before | 775496pps | 428614pps
> After | 1109316pps | 742853pps
>
> In the 6.11, we disabled this feature because a regress [1].
>
> Now, we fix the problem and re-enable it.
>
> [1]:
> http://lore.kernel.org/all/8b20cc28-45a9-4643-8e87-ba164a540...@oracle.com
>
> Signed-off-by: Xuan Zhuo <xuanz...@linux.alibaba.com>
> ---
> drivers/net/virtio_net.c | 17 +++++++++++++++++
> 1 file changed, 17 insertions(+)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index cd90e77881df..8cf24b7b58bd 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -6133,6 +6133,21 @@ static int virtnet_alloc_queues(struct virtnet_info
> *vi)
> return -ENOMEM;
> }
>
> +static void virtnet_rq_set_premapped(struct virtnet_info *vi)
> +{
> + int i;
> +
> + /* disable for big mode */
> + if (vi->mode == VIRTNET_MODE_BIG)
> + return;
Nitpick: I would like such a check to be done at the caller.
But anyhow the patch looks good
Acked-by: Jason Wang <jasow...@redhat.com>
Thanks
> +
> + for (i = 0; i < vi->max_queue_pairs; i++) {
> + /* error should never happen */
> + BUG_ON(virtqueue_set_dma_premapped(vi->rq[i].vq));
> + vi->rq[i].do_dma = true;
> + }
> +}
> +
> static int init_vqs(struct virtnet_info *vi)
> {
> int ret;
> @@ -6146,6 +6161,8 @@ static int init_vqs(struct virtnet_info *vi)
> if (ret)
> goto err_free;
>
> + virtnet_rq_set_premapped(vi);
> +
> cpus_read_lock();
> virtnet_set_affinity(vi);
> cpus_read_unlock();
> --
> 2.32.0.3.g01195cf9f
>
